Method for manufacturing surface acoustic wave device

ABSTRACT

Provided is a method of manufacturing surface acoustic wave (SAW) devices having a first conductive pattern and a second conductive pattern of different thicknesses on one piezoelectric substrate. Combination of a plurality of steps of forming metal films and etching steps allows accurate production of SAW devices having a plurality of electrodes of different thicknesses on one piezoelectric substrate.

TECHNICAL FIELD

[0001] The present invention relates to a method of manufacturing asurface acoustic wave (SAW) device and a method of measuring a filmthickness in a electric component such as a SAW device.

BACKGROUND ART

[0002] A conventionally used method of forming independent SAW devicesaccommodating to a plurality of frequencies on one substrate is making aplurality of electrode patterns having the same thickness at differentintervals. When a plurality of SAW devices having significantlydifferent frequencies are formed by this method, it is extremelydifficult to design and manufacture a plurality of patterns havingdifferent intervals between the electrodes under optimum conditions ofeach pattern.

[0003] As means of addressing this problem, the Japanese PatentUnexamined Publication No. H10-93369 discloses a method of laminating aplurality of kinds of metals having significantly different etchingspeeds, and forming a plurality of SAW devices having differentthicknesses by utilizing the difference in etching speeds.

[0004] However, for the method of utilizing the difference in etchingspeeds, combinations of metals having large difference in etching speedsare limited and thus the design of electrode patterns is restricted.Additionally, when a metal film is dry-etched, a part of the metal filmwithout a photo-resist layer is susceptible to damage. On the otherhand, when a metal film is wet-etched, the side faces of the metal filmare affected by the etching. Therefore, by any one of the etchingmethods, accurate formation of electrode patterns is difficult. For thisreason, variations in frequency increase.

DISCLOSURE OF THE INVENTION

[0005] A first metal film is formed on a piezoelectric substrate. Byetching the first metal film, a bottom part of a first conductivepattern is formed. A second metal film is formed on the side of thepiezoelectric substrate having the bottom part of the first conductivepattern. Further, a third metal film is formed on the second metal film.By etching these first metal film, second metal film, and third metalfilm, the first conductive pattern and a second conductive pattern areformed. This method reduces deviation from a target frequency andvariations in frequency in a plurality of SAW devices that have metalfilms of different thicknesses on one piezoelectric substrate andaccommodate to different frequencies.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIGS. 1A through 1F are sectional views of a surface acoustic wave(SAW) filter in accordance with a first exemplary embodiment of thepresent invention, showing a manufacturing process thereof.

[0007]FIGS. 2A through 2E are sectional views of a SAW filter inaccordance with a second exemplary embodiment of the present invention,showing a manufacturing process thereof.

[0008]FIGS. 3A through 3H are sectional views of a SAW filter inaccordance with a third exemplary embodiment of the present invention,showing a manufacturing process thereof.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS First Exemplary Embodiment

[0009] A manufacturing method of a first exemplary embodiment isdescribed with reference to FIGS. 1A through 1F.

[0010] As shown in FIG. 1A, first metal film 2, e.g. a 250-nm-thickCu-containing Al layer, is formed on piezoelectric substrate 1 made ofLiTaO₃ or other material, by sputtering.

[0011] Next, photo-resist layer 3 is applied to first metal film 2.After a desired pattern is exposed to light and developed byphoto-lithography, bottom part 4 of a first conductive pattern is formedby wet etching, as shown in FIG. 1B. Now, bottom part 4 of the firstconductive pattern refers to an area of the first metal film existingbefore the final shape of the first conductive pattern is formed.

[0012] Next, after photo-resist layer 3 is peeled off, second metal film5, e.g. a 10-nm-thick Ti-containing layer, is formed on the side ofpiezoelectric substrate 1 having bottom part 4 of the first conductivepattern formed thereon by sputtering, as shown in FIG. 1C. On the secondmetal film, third metal film 6, e.g. an 80-nm-thick Al-containing layer,is formed by sputtering.

[0013] Next, photo-resist layer 7 is applied to third metal film 6.After a desired pattern is exposed to light and developed byphoto-lithography, second conductive pattern 8 is formed by dry etching,as shown in FIG. 1D. Then, the photo-resist layer is peel off to providehigh-frequency surface acoustic wave (SAW) filter 11 made of secondconductive pattern 8 first.

[0014] Next, photo-resist layer 9 is applied to the entire surface.While the second conductive pattern is protected, a desired pattern isexposed to light and developed-by photo-lithography. Then, as shown inFIG. 1E, first conductive pattern 10 is formed by dry etching.

[0015] Next, photo-resist layer 9 is peeled off to provide low-frequencySAW filter 12 made of first conductive pattern 10 as shown in FIG. 1F,after the second conductive pattern.

[0016] In this manner, two kinds of SAW devices that have metal films ofdifferent thicknesses on one piezoelectric substrate 1 are formed sothat thinner second conductive pattern 8 is formed first, and thickerfirst conductive pattern 10 is formed next. Thus, metal films havingdifferent thicknesses are formed on one piezoelectric substrate bycombination of formation of a plurality of metal films and etching. Thismethod can reduce deviation from a target frequency and variations infrequency in a plurality of SAW devices accommodating to differentfrequencies. Thereafter, cutting the patterns into a predetermineddimension divides the patterns into pieces of SAW devices.

[0017] In this embodiment, the thickness ratio of first conductivepattern 10 with respect to second conductive pattern 8 is approx. 3.8.When a plurality of conductive patterns having different thicknesses areformed on one piezoelectric substrate 1, formation of conductivepatterns having large difference in thickness at the same time is proneto decrease accuracy of conductive patterns. Especially when thethickness ratio of conductive patterns exceeds 2.0, the accuracy of theconductive patterns decreases. However, in this embodiment, theconductive patterns are formed independently. This method increases theaccuracy of conductive patterns.

[0018] In this embodiment, the center frequency of low-frequency SAWfilter 12 is 900 MHz and that of high-frequency SAW filter 11 is 1.4GHz. Now, first conductive pattern 10 and second conductive pattern 8include comb-shaped electrodes, reflector electrodes, lead electrodes,and pad electrodes for forming low-frequency SAW filter 12 andhigh-frequency SAW filter 11, respectively.

[0019] The present invention is devised by aiming at the following twopoints. To reduce deviation from a target frequency and variations infrequency, variations in the thickness of the conductive patterns anddamages thereto should be reduced. These influences are larger at ahigher target frequency.

[0020] The optimum conditions for etching a metal film varies with thethickness of the metal film. For this reason, when a thicker metal filmand a thinner metal film are etched at the same time, the etchingconditions of either of the metal films are out of the optimumconditions thereof. Thus, the accuracy of the film thickness decreases.To avoid the decrease in accuracy, second conductive pattern 8 forhigh-frequency having thinner metal films is formed first. Etching underthe conditions suitable for the thinner films reduces damages topiezoelectric substrate 1. Additionally, first conductive pattern 10 isformed after second conductive pattern 8 is protected using photo-resistlayer 9. This step can reduce damages to the film thickness of secondconductive pattern 8 and piezoelectric substrate 1. These reducedeviation from a target frequency and variations in frequency in SAWdevices.

[0021] Next etching step is performed after second conductive pattern 8is protected by a photo-resist layer. These steps prevent deviation froma target frequency and variations in frequency in thinner secondconductive pattern 8 from significantly increasing.

[0022] Additionally, in the step of forming the metal films, sputteringis used. This process allows formation of a homogeneous metal filmhaving excellent orientation and few variations in thickness, thusreducing deviation from a target frequency and variations in frequency.

[0023] Further, in the step of etching first metal film 2, wet etchingis used. This process can efficiently etch a thick metal film for ashort period of time. This causes almost no damages to piezoelectricsubstrate 1. Because only first metal film 2 is formed on the substrate,no damages are caused to second metal film 5 and third metal film 6.

[0024] In the step of etching second metal film 5 and third metal film6, dry etching is used. This process forms second conductive pattern 8at high accuracy, thus reducing deviation from a target frequency andvariations in frequency in high-frequency SAW filter 11.

[0025] Additionally, for second metal film 5, a material different fromthose of first metal film 2 and third metal film 6 is used. Thisimproves orientation between respective metal films and adhesiveproperty therebetween. Thus, adhesive property between first conductivepattern 10 and second conductive pattern 8 and electric strength thereofare improved.

[0026] In this embodiment, LiTaO₃ is used for piezoelectric substrate 1.However, any piezoelectric material can be used.

[0027] In this embodiment, wet etching is used as the etching method forforming bottom part 4 of first conductive pattern 10. In reducing a lossin a SAW device, wet etching is effective. In reducing deviation from atarget frequency and controlling variations in frequency, dry etching iseffective. For these reasons, it is desirable to select either oneaccording to the purpose.

[0028] Additionally, it is desirable to form a protective layer, e.g. a30-nm-thick Al₂O₃-containing layer, on first conductive pattern 10 andsecond conductive pattern 8 by an anodizing process. This protectivelayer prevents deterioration of the property and short circuits evenwhen electrically conductive foreign substances adhere to firstconductive pattern 10 or second conductive pattern 8. This layer alsoinhibits corrosion and alteration of metal films even when moisture orgas enters into the patterns. Therefore, initial failure is reduced, andreliability, such as weathering performance, is improved.

[0029] Materials of the protective layer include SiO₂, Si, and siliconnitride in addition to Al₂O₃. The protective layer can be provided onthe entire surface of first conductive pattern 10 and second conductivepattern 2, the entire surface or a part thereof except pad electrodesfor external connection, or the entire surface or a part thereof onpiezoelectric substrate 1. However, to reduce a loss in a SAW device, itis desirable provide no protective layer on piezoelectric substrate 1.

[0030] In this embodiment, Cu-containing Al is used as the material offirst metal film 2. However, Al alloys containing metals other than Cuor Al, e.g. Al-Ti, Al-W, and Al-Ta, can also be used. Ti (Titanium) isused as the material of second metal film 5. However, metals and alloysthat improve adhesive property between a plurality of kinds of metalslaminated on each other can be used. Such metals and alloys include Tialloys, Cr and Cr alloys, Ta and Ta alloys, W and W alloys, Ni and Nialloys, Mo and Mo alloys, and Mg and Mg alloys. Al (Aluminum) is used asthe material of third metal film 6. In addition to Al, Al alloys, e.g.Al-Ti, Al-W, and Al-Ta, can also be used.

[0031] The material of first metal film 2 and the material of thirdmetal film 6 can be the same or different from each other.

[0032] As for piezoelectric substrate 1 having first metal film 2 formedthereon, it is desirable to measure the thickness of first metal film 2,using a fluorescent X-ray analyzer, for example, and give feedback onany deviation from a target value to sputtering conditions forcorrection.

[0033] Further, the thickness of the portion having only second metalfilm 5 and third metal film 6 on piezoelectric substrate 1 is measured,using a fluorescent X-ray analyzer, for example, in a state with bottompart 4 of the first conductive pattern, second metal film 5, and thirdmetal film 6 formed. Then, the measurement of the total thickness ofsecond metal film 5 and third metal film 6 are separated to obtain thethickness of second metal film 5 and the thickness of third metal film 6according to the wavelengths of the fluorescent X-rays. When anydeviation from a target value is found, feedback is given to thesputtering conditions for correction.

[0034] The measurement of the thicknesses of the films on piezoelectricsubstrate 1 is performed in the center of piezoelectric substrate 1.This enables to control the thickness of metal films, ensuringproductivity, without reducing the number of SAW devices onpiezoelectric substrate 1. As the area in which the film thickness ismeasured on piezoelectric substrate 1, it is desirable to ensure an areain which a uniform thickness is ensured with little influence of stepsin the vicinity of the area. It is also desirable to provide a pluralityof points of measurement. This allows measurement of distribution of thethickness of metal films on piezoelectric substrate 1. Thus, thethickness of metal films is accurately controlled in the direction ofthe surface of piezoelectric substrate 1.

[0035] Even when only second metal film 5 is formed on bottom part 4 offirst conductive pattern, the thickness of second metal film 5 can beobtained by performing fluorescent X-lay analysis of the portion havingonly second metal film 5 on piezoelectric substrate 1.

[0036] When the area having second metal film 5 and third metal film 6formed on piezoelectric substrate 1 is small, influence of other metals,e.g. bottom part 4 of first conductive pattern, deteriorates measurementaccuracy in fluorescent X-ray analysis in some cases. In such a case,the second metal film and the third metal film are formed anotherpiezoelectric substrate by sputtering under the same conditions, and thethicknesses of the second and third films formed on the piezoelectricsubstrate are measured using a fluorescent X-ray analyzer. Thus, thethicknesses of second metal film 5 and third metal film 6 onpiezoelectric substrate 1 can be obtained.

[0037] In this method of measuring the thickness, the thicknesses of aplurality of kinds of metal films are measured during a manufacturingprocess. Thus, the thicknesses of the metal films can be controlledaccurately. This can improve the target property of an electroniccomponent with respect to high frequency, e.g. reducing deviation from atarget frequency and variations in frequency.

Second Exemplary Embodiment

[0038] A manufacturing method in accordance with a second exemplaryembodiment is described with reference to FIGS. 2A through 2E.Components similar to those described in the first exemplary embodimentare denoted with the same reference marks, and the descriptions of thosecomponents are omitted.

[0039] The steps shown in FIG. 2A through 2C are similar to those shownin FIGS. 1A through 1C. In the steps shown in FIGS. 2A through 2C,bottom part 4 of a first conductive pattern is formed on piezoelectricsubstrate 1, and second metal film 5 and third metal film 6 are formedon the side of the piezoelectric substrate having the bottom part.

[0040] Next, photo-resist layer 7 is applied to third metal film 6.Desired patterns are exposed to light and developed byphoto-lithography. Thereafter, third metal film 6, second metal film 5,and bottom part 4 of the first conductive pattern are dry-etched to formfirst conductive pattern 10 and second conductive pattern 8 at the sametime, as shown in FIG. 2D.

[0041] Next, as shown in FIG. 2E, photo-resist layer 7 is peeled off toform low-frequency surface acoustic wave (SAW) filter 12 made of firstconductive pattern 10 and high-frequency SAW filter 11 made of secondconductive pattern 8, at the same time.

[0042] Thus, two kinds of SAW devices having metal films of differentthicknesses are formed on one piezoelectric substrate 1 at the sametime. Forming metal films having different thicknesses on onepiezoelectric substrate by combination of formation of a plurality ofmetal films and etching reduces deviation from a target frequency andvariations in frequency in a plurality of SAW devices accommodating tovarious frequencies. Thereafter, the plurality of devices is cut into apredetermined dimension to provide respective pieces of SAW devices.

[0043] When a thick metal film and a thin metal film are etchedindependently, the etching process must be performed at least twice.However, the optimum etching conditions vary with the thickness of themetal film. For this reason, the metal film and piezoelectric substrateare considerably influenced by etching. This increases deviation from atarget frequency and variations in frequency in some cases.

[0044] For the present invention, to avoid the above problems, a thickmetal film and a thin metal film are etched at the same time, andreduction in the number of etching processes reduces the influence ofetching, and thus deviation from a target frequency and variations infrequency.

[0045] The influence of etching is specifically described hereinafter.During etching, the properties may vary even under the etchingconditions of set values. This is because every etching process isinfluenced by circumstance conditions and thus some etching processesare excessive over the set values and the other etching processes areinsufficient. In every etching process, the influence subtly changes.For this reason, when etching processes are performed a plurality oftimes, the first etching process is excessive and the second etchingprocess is insufficient, for example. In this case, the influence of theetching processes on the metal films and a piezoelectric substrate areso complicated that a simple correction cannot be made.

[0046] However, when the etching process is performed only once, theinfluence thereof can easily be corrected.

[0047] Thus, reducing the number of etching processes can control aplurality of metal films having different thicknesses accurately, andreduce deviation from a target frequency and variations in frequency.Such an effect is more obvious when a plurality of metal films havingsimilar thicknesses is formed because metal films having similarthicknesses are significantly influenced by etching.

[0048] Additionally, reducing the number of etching processes reducesthe number of heat treatment after application of a photo-resist layer.This reduces generation of static electricity, electrostatic dischargedamage, or the like caused by the heat treatment. Thus, the yield andreliability of the devices can be improved.

[0049] Further, reducing the number of etching processes can reduce thenumber of man-hour and plant investment, thus allowing cost reduction.

Third Exemplary Embodiment

[0050] A manufacturing method in accordance with a third exemplaryembodiment is described with reference to FIGS. 3A through 3H.Components similar to those described in the first exemplary embodimentare denoted with the same reference marks, and the descriptions of thosecomponents are omitted.

[0051] In FIG. 3, the steps shown in FIGS. 3A through 3F are similar tothose shown in FIGS. 1A through 1F. Second conductive pattern 14 andfirst conductive pattern 13 are formed on piezoelectric substrate 1.However, in this structure, a part of the second conductive pattern isconnected to a part of the first conductive pattern.

[0052] Next, photo-resist layer 22 is applied to the entire surface.While second conductive pattern 14 and the part except pad electrodes 19and 21 in first conductive pattern 13 are protected, desired patternsare exposed to light and developed by photolithography. Further, fourthmetal film 17, e.g. a 100-nm-thick Ti-containing layer, is formed on thephoto-resist layer by vapor deposition. As shown in FIG. 3G, fifth metalfilm 18, e.g. a 300-nm-thick Al-containing layer, is formed on thefourth metal film. Thereafter, as shown in FIG. 3H, photo-resist layer22 and the fourth metal film and the fifth meal film formed onphoto-resist layer 22 are removed by lift-off to form fourth metal film17 and fifth metal film 18 on first conductive pattern 13. Next, thepatterns are cut into a predetermined dimension to provide pieces ofsurface acoustic wave (SAW) devices. Thereafter, a piece of SAW devicesobtained in this manner is disposed on the bottom of a package or thelike, and a pad electrode and a terminal electrode connection on thepackage are connected via a bonding wire, bump, and the like. Then, thepackage is sealed to provide an electronic component.

[0053] In the first exemplary embodiment, first conductive pattern 10 isstructured so that the first, second, and third metal films arelaminated and second conductive pattern 8 is structured so that thesecond and third metal films are laminated. The first and secondconductive patterns are independently formed.

[0054] On the other hand, the third exemplary embodiment includes:

[0055] 1) lead electrode 15, a part of first conductive pattern 13,connected to second conductive pattern 14;

[0056] 2) pattern 16, a part of second conductive pattern 14, connectedto first conductive pattern 13; and

[0057] 3) pad electrode 19 connected to lead electrode 15 and made of apart of first conductive pattern 13. In pad electrode 19, fourth metalfilm 17 is formed on third metal film 6, and fifth metal film 18 isfurther formed on the fourth metal film.

[0058] The third exemplary embodiment further includes:

[0059] 4) lead electrode 20 made of a part of first conductive pattern13; and

[0060] 5) pad electrode 21 connected to lead electrode 20 and made of apart of first conductive pattern 13. In pad electrode 21, fourth metalfilm 17 is formed on third metal film 6, and fifth metal film 18 isfurther formed on the fourth metal film.

[0061] In production of such an electronic component, a piece of SAWdevices can be mounted on a mounting substrate of the same shape anddimension as the piece via a bump or conductive paste to provide a chipsize package (CSP).

[0062] Shown in the third exemplary embodiment is a structure in whichfourth metal film 17 and fifth metal film 18 are formed on firstconductive pattern 13 to provide lead electrode 20 and pad electrode 21.Besides this structure, the fourth metal film and fifth metal film areprovided on second conductive pattern 14 and the lead electrode or padelectrode is provided on second conductive pattern 14.

[0063] As described above, in the third exemplary embodiment, leadelectrode 20 and pad electrode 21 are provided to connect with first SAWdevice 23 and lead electrode 15 and pad electrode 19 are provided toconnect with second SAW device 24. This structure thickens not onlyfirst SAW device 23 but also lead electrode 15 of thin second SAW device24. This reduces connection impedance with respect to an externalconnection terminal and thus a loss in the SAW devices. As obvious fromFIG. 3H, lead electrode 15 includes neither fourth metal film 17 norfifth meal film 18. However, lead electrode 15 is thick even without thestep of providing fourth metal film 17 and fifth metal film 18.

[0064] Providing fifth metal film 18 in pad electrode 19 and padelectrode 21 via fourth metal film 17 increases the bonding strength andelectric strength of the electrodes.

[0065] Fourth metal film 17 not only improves adhesion of a plurality oflaminated metal films but also prevents a decrease in the bondingstrength of the electrode when an external connection terminal isconnected onto fifth meal film 18. For example, when an Au bump isprovided on fifth metal film 18 for connection with an externalconnection terminal, Au in the Au bump has properties of diffusing infifth metal film 18 and deteriorating the bonding strength of theelectrode. Fourth metal film 17 prevents diffusion of Au and increasesthe bonding strength of the electrode, thus preventing peeling of theelectrode at bonding.

[0066] As described above, the materials of second metal film 5 andfourth metal film 17 are similar to each other; however, the purpose ofproviding them is obviously different. The two metal films haverespective advantages of their own.

[0067] Additionally, forming fifth metal film 18 by vapor deposition canprovide a soft metal film on the uppermost layer. This soft metal filmincreases the bonding strength with respect to an external connectionterminal, e.g. a bonding wire and a bump, and reduces contactresistance. This can reduce a loss in a SAW device, and improve thebonding reliability and life thereof.

[0068] In the above description, the fourth and fifth metal films areformed after the production of the first and second conductive patternsin accordance with the first exemplary embodiment. However, the sameadvantage can be obtained by the method described in the secondexemplary embodiment instead of the first exemplary embodiment.

INDUSTRIAL APPLICABILITY

[0069] As described above, in accordance with the present invention,surface acoustic wave (SAW) devices having different thicknesses areformed on one piezoelectric substrate so that a thinner SAW device isformed first or both SAW devices are formed at the same time. Metalfilms are formed by sputtering. First, the bottom part of a firstconductive pattern is formed by etching. Next, the other conductivepatterns are formed by etching. This method allows accurate formation ofthe conductive patterns. This can reduce deviation from a targetfrequency and variations in frequency and especially realize ahigh-frequency SAW filter of higher performance. Additionally, thedevice is structured to have a thick lead electrode and a thick padelectrode. This structure can increase the bonding strength with respectto an external connection terminal, and reduce contact resistance. Thiscan reduce a loss in the SAW device, and increase the bondingreliability and life thereof.

[0070] Reference Marks in the Drawings

[0071]1 Piezoelectric substrate

[0072]2 First metal film

[0073]3 Photo-resist layer

[0074]4 Bottom part of first conductive pattern

[0075]5 Second metal film

[0076]6 Third metal film

[0077]7 Photo-resist layer

[0078]8 Second conductive pattern

[0079]9 Photo-resist layer

[0080]10 First conductive pattern

[0081]11 High-frequency surface acoustic wave filter

[0082]12 Low-frequency surface acoustic wave filter

[0083]13 First conductive pattern

[0084]14 Second conductive pattern

[0085]15 Lead electrode

[0086]16 A part of second conductive pattern connected to firstconductive pattern

[0087]17 Fourth metal film

[0088]18 Fifth metal film

[0089]19 Pad electrode

[0090]20 Lead electrode

[0091]21 Pad electrode

[0092]22 Photo-resist layer

[0093]23 First surface acoustic wave device

[0094]24 Second surface acoustic wave device

1. A method of manufacturing a surface acoustic wave (SAW) devicecomprising steps of: forming a first metal film on a piezoelectricsubstrate; forming a bottom part of a first conductive pattern byetching the first metal film; forming a second metal film on a side ofthe piezoelectric substrate having the bottom part of the firstconductive pattern; forming a third metal film on the second metal film;and forming the first conductive pattern and a second conductive patternby etching the first metal film, the second metal film and the thirdmetal film.
 2. The method of manufacturing a SAW device of claim 1,wherein said step of forming the first conductive pattern and the secondconductive pattern comprise the sub-steps of: forming the secondconductive pattern by etching the second metal film and the third metalfilm existing in an area other than an area having the bottom part ofthe first conductive pattern; and forming the first conductive patternby etching the third metal film, the second metal film and the firstmetal film in the area having the bottom part of the first conductivepattern.
 3. The method of manufacturing a SAW device of claim 1, whereinthe second conductive pattern is formed before the first conductivepattern.
 4. The method of manufacturing a SAW device of claim 1, whereinthe first conductive pattern and the second conductive pattern areformed at the same time in said step of forming the first conductivepattern and the second conductive pattern.
 5. The method ofmanufacturing a SAW device of claim 1, wherein the first conductivepattern is formed thicker than the second conductive pattern.
 6. Themethod of manufacturing a SAW device of claim 1, wherein at least one ofthe first metal film, the second metal film, and the third metal film isformed by sputtering.
 7. The method of manufacturing a SAW device ofclaim 1, wherein the bottom part of the first conductive pattern isformed by wet etching.
 8. The method of manufacturing a SAW device ofclaim 1, wherein at least one of the first conductive pattern and thesecond conductive pattern is formed by dry etching.
 9. The method ofmanufacturing a SAW device of claim 1, wherein the first metal filmcontains at least Al as a component thereof.
 10. The method ofmanufacturing a SAW device of claim 1, wherein the second metal film ismade of a metal material highly adherent to the first metal film. 11.The method of manufacturing a SAW device of claim 1, wherein the secondmetal film contains at least one of Ti, Cr, Ta, W, Ni, Mo, and Mg, as acomponent thereof.
 12. The method of manufacturing a SAW device of claim1, wherein the third metal film contains at least Al as a componentthereof.
 13. The method of manufacturing a SAW device of claim 1,further comprising a step of providing a protective film on at least apart of at least one of the first conductive pattern and the secondconductive pattern.
 14. The method of manufacturing a SAW device ofclaim 1, wherein a thickness ratio of the first conductive pattern andthe second conductive pattern with respect to a thinner pattern is atleast two.
 15. The method of manufacturing a SAW device of claim 1,wherein a center frequency of the SAW device formed of at least one ofthe first conductive pattern and the second conductive pattern is atleast 1 GHz.
 16. The method of manufacturing a SAW device of claim 1,further comprising steps of: forming a fourth metal film on at least oneof the first conductive pattern and the second conductive pattern;forming a fifth metal film on the fourth metal film; and forming apattern in the fifth metal film and the fourth metal film.
 17. Themethod of manufacturing a SAW device of claim 16, wherein at least oneof the fourth metal film and the fifth meal film is formed by vapordeposition.
 18. The method of manufacturing a SAW device of claim 16,wherein said step of forming a pattern in the fifth metal film and thefourth metal film includes a sub-step of lifting off a photo-resistlayer and the fourth metal film and the fifth metal film formed on thephoto-resist layer.
 19. The method of manufacturing a SAW device ofclaim 1, wherein a part of the first conductive pattern is coupled to apart of the second conductive pattern.
 20. The method of manufacturing aSAW device of claim 19, wherein the part of the first conductive patterncoupled to the part of the second conductive pattern is one of a leadelectrode and a pad electrode for connection to an external terminal.21. The method of manufacturing a SAW device of claim 16, wherein a partof one of the first conductive pattern and the second conductive patternhaving the fourth metal film and the fifth metal film formed thereon isone of a lead electrode and a pad electrode for connection to anexternal terminal.
 22. The method of manufacturing a SAW device of claim16, wherein the fourth metal film is made of a material for inhibitingdiffusion of a metal that forms an external terminal coupled to thefifth metal film.
 23. The method of manufacturing a SAW device of claim16, wherein the fourth metal film contains at least one of Ti, Cr, Ta,W, Ni, Mo, and Mg, as a component thereof.
 24. The method ofmanufacturing a SAW device of claim 16, wherein the fifth metal filmcontains at least Al as a component thereof.
 25. The method ofmanufacturing a SAW device of claim 1, further comprising steps of:forming an area without the first metal film in said step of forming thebottom part of the first conductive pattern; measuring a thickness ofthe first metal film after said step of forming the first metal film;and measuring a thickness of a metal film in the area without the firstmetal film after said step of forming the second metal film.
 26. Themethod of manufacturing a SAW device of claim 25, wherein said step ofmeasuring the thickness of the metal film in the area without the firstmeal film is performed immediately after at least one of said steps offorming the second metal film and forming the third metal film.
 27. Themethod of manufacturing a SAW device of claim 25, wherein the areawithout the first metal film is provided in a center of thepiezoelectric substrate.
 28. The method of manufacturing a SAW device ofclaim 25, wherein the area without the first metal film is provided in aplurality positions on the piezoelectric substrate.